This invention pertains to earthworking tool bits, especially coal mining tool bits, which utilize hard wear resistant inserts mounted in a forward working portion of the bit and supported by parent material surrounding the insert.
In tool bits of the prior art, it is known that using hard wear resistant inserts formed of cemented hard metal carbides can greatly enhance the tool life of earthworking bits, especially the bits used in coal mining operations.
The earthworking bits have a forward working portion which is designed for impacting and fracturing earth formations and the inserts are used on the tip of the tool bit so as to reduce wear on the bit due to impact and abrasiveness of earth formations. The inserts are supported and held in place by the surrounding parent material of the forward working portion of the bit, and when properly supported in the parent material, can greatly enhance the wear life of the tool bit.
It is the goal when using such an insert tipped tool bit that the wear life of the tool will equal the wear life of the insert material itself. Since such inserts are usually formed of a cemented hard metal carbide material, such as tungsten carbide, such a tool would then have an extremely long life.
Part of the problem in trying to achieve the above-mentioned goal of the tool bit life lasting as long as the insert material is the erosion of the parent material supporting the insert. Final wear failure of a tool bit is caused by the loss of the wear resistant insert due to the insert breaking off or separating from the parent material. Usually, this occurs because most of the parent has been washed away and the securing force on the insert is weakened or destroyed.
The prior art approaches to hold the insert secured in the tool for the life of the insert material have centered around either providing a sufficient amount of parent material to be eroded away or trying to protect the parent material by various surface hardening techniques. While these have all had some moderate success, it is believed that the present invention will provide long lasting tool life.
It is an object of the present invention to provide a tool bit with a longer useful life than generally known heretofore.
It is a further object of the present invention to provide a method whereby earthworking tools having insert tipped forward working portions may be provided with a longer useful life by a very simple and efficient means.